/*
 * $Header:
 * /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons
 * //httpclient/src/java/org/apache/commons/httpclient/util/EncodingUtil.java,v
 * 1.8 2004/05/13 04:01:22 mbecke Exp $ $Revision: 480424 $ $Date: 2006-11-29
 * 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many individuals on
 * behalf of the Apache Software Foundation. For more information on the Apache
 * Software Foundation, please see <http://www.apache.org/>.
 */
package com.microsoft.tfs.core.httpclient.util;

import java.io.UnsupportedEncodingException;

import org.apache.commons.codec.net.URLCodec;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.microsoft.tfs.core.httpclient.HttpClientError;
import com.microsoft.tfs.core.httpclient.NameValuePair;

/**
 * The home for utility methods that handle various encoding tasks.
 *
 * @author Michael Becke
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 *
 * @since 2.0 final
 */
public class EncodingUtil {

    /** Default content encoding chatset */
    private static final String DEFAULT_CHARSET = "ISO-8859-1";

    /** Log object for this class. */
    private static final Log LOG = LogFactory.getLog(EncodingUtil.class);

    /**
     * Form-urlencoding routine.
     *
     * The default encoding for all forms is
     * `application/x-www-form-urlencoded'. A form data set is represented in
     * this media type as follows:
     *
     * The form field names and values are escaped: space characters are
     * replaced by `+', and then reserved characters are escaped as per [URL];
     * that is, non-alphanumeric characters are replaced by `%HH', a percent
     * sign and two hexadecimal digits representing the ASCII code of the
     * character. Line breaks, as in multi-line text field values, are
     * represented as CR LF pairs, i.e. `%0D%0A'.
     *
     * <p>
     * if the given charset is not supported, ISO-8859-1 is used instead.
     * </p>
     *
     * @param pairs
     *        the values to be encoded
     * @param charset
     *        the character set of pairs to be encoded
     *
     * @return the urlencoded pairs
     *
     * @since 2.0 final
     */
    public static String formUrlEncode(final NameValuePair[] pairs, final String charset) {
        try {
            return doFormUrlEncode(pairs, charset);
        } catch (final UnsupportedEncodingException e) {
            LOG.error("Encoding not supported: " + charset);
            try {
                return doFormUrlEncode(pairs, DEFAULT_CHARSET);
            } catch (final UnsupportedEncodingException fatal) {
                // Should never happen. ISO-8859-1 must be supported on all JVMs
                throw new HttpClientError("Encoding not supported: " + DEFAULT_CHARSET);
            }
        }
    }

    /**
     * Form-urlencoding routine.
     *
     * The default encoding for all forms is
     * `application/x-www-form-urlencoded'. A form data set is represented in
     * this media type as follows:
     *
     * The form field names and values are escaped: space characters are
     * replaced by `+', and then reserved characters are escaped as per [URL];
     * that is, non-alphanumeric characters are replaced by `%HH', a percent
     * sign and two hexadecimal digits representing the ASCII code of the
     * character. Line breaks, as in multi-line text field values, are
     * represented as CR LF pairs, i.e. `%0D%0A'.
     *
     * @param pairs
     *        the values to be encoded
     * @param charset
     *        the character set of pairs to be encoded
     *
     * @return the urlencoded pairs
     * @throws UnsupportedEncodingException
     *         if charset is not supported
     *
     * @since 2.0 final
     */
    private static String doFormUrlEncode(final NameValuePair[] pairs, final String charset)
        throws UnsupportedEncodingException {
        final StringBuffer buf = new StringBuffer();
        for (int i = 0; i < pairs.length; i++) {
            final URLCodec codec = new URLCodec();
            final NameValuePair pair = pairs[i];
            if (pair.getName() != null) {
                if (i > 0) {
                    buf.append("&");
                }
                buf.append(codec.encode(pair.getName(), charset));
                buf.append("=");
                if (pair.getValue() != null) {
                    buf.append(codec.encode(pair.getValue(), charset));
                }
            }
        }
        return buf.toString();
    }

    /**
     * Converts the byte array of HTTP content characters to a string. If the
     * specified charset is not supported, default system encoding is used.
     *
     * @param data
     *        the byte array to be encoded
     * @param offset
     *        the index of the first byte to encode
     * @param length
     *        the number of bytes to encode
     * @param charset
     *        the desired character encoding
     * @return The result of the conversion.
     *
     * @since 3.0
     */
    public static String getString(final byte[] data, final int offset, final int length, final String charset) {

        if (data == null) {
            throw new IllegalArgumentException("Parameter may not be null");
        }

        if (charset == null || charset.length() == 0) {
            throw new IllegalArgumentException("charset may not be null or empty");
        }

        try {
            return new String(data, offset, length, charset);
        } catch (final UnsupportedEncodingException e) {

            if (LOG.isWarnEnabled()) {
                LOG.warn("Unsupported encoding: " + charset + ". System encoding used");
            }
            return new String(data, offset, length);
        }
    }

    /**
     * Converts the byte array of HTTP content characters to a string. If the
     * specified charset is not supported, default system encoding is used.
     *
     * @param data
     *        the byte array to be encoded
     * @param charset
     *        the desired character encoding
     * @return The result of the conversion.
     *
     * @since 3.0
     */
    public static String getString(final byte[] data, final String charset) {
        return getString(data, 0, data.length, charset);
    }

    /**
     * Converts the specified string to a byte array. If the charset is not
     * supported the default system charset is used.
     *
     * @param data
     *        the string to be encoded
     * @param charset
     *        the desired character encoding
     * @return The resulting byte array.
     *
     * @since 3.0
     */
    public static byte[] getBytes(final String data, final String charset) {

        if (data == null) {
            throw new IllegalArgumentException("data may not be null");
        }

        if (charset == null || charset.length() == 0) {
            throw new IllegalArgumentException("charset may not be null or empty");
        }

        try {
            return data.getBytes(charset);
        } catch (final UnsupportedEncodingException e) {

            if (LOG.isWarnEnabled()) {
                LOG.warn("Unsupported encoding: " + charset + ". System encoding used.");
            }

            return data.getBytes();
        }
    }

    /**
     * Converts the specified string to byte array of ASCII characters.
     *
     * @param data
     *        the string to be encoded
     * @return The string as a byte array.
     *
     * @since 3.0
     */
    public static byte[] getAsciiBytes(final String data) {

        if (data == null) {
            throw new IllegalArgumentException("Parameter may not be null");
        }

        try {
            return data.getBytes("US-ASCII");
        } catch (final UnsupportedEncodingException e) {
            throw new HttpClientError("HttpClient requires ASCII support");
        }
    }

    /**
     * Converts the byte array of ASCII characters to a string. This method is
     * to be used when decoding content of HTTP elements (such as response
     * headers)
     *
     * @param data
     *        the byte array to be encoded
     * @param offset
     *        the index of the first byte to encode
     * @param length
     *        the number of bytes to encode
     * @return The string representation of the byte array
     *
     * @since 3.0
     */
    public static String getAsciiString(final byte[] data, final int offset, final int length) {

        if (data == null) {
            throw new IllegalArgumentException("Parameter may not be null");
        }

        try {
            return new String(data, offset, length, "US-ASCII");
        } catch (final UnsupportedEncodingException e) {
            throw new HttpClientError("HttpClient requires ASCII support");
        }
    }

    /**
     * Converts the byte array of ASCII characters to a string. This method is
     * to be used when decoding content of HTTP elements (such as response
     * headers)
     *
     * @param data
     *        the byte array to be encoded
     * @return The string representation of the byte array
     *
     * @since 3.0
     */
    public static String getAsciiString(final byte[] data) {
        return getAsciiString(data, 0, data.length);
    }

    /**
     * This class should not be instantiated.
     */
    private EncodingUtil() {
    }

}
